The present invention relates generally to voltage regulation in power supplies for electrical circuits, such as in amplifiers. The invention further relates to control of resonance in an electronic circuit, such as an amplifier. More particularly, the invention relates to amplifiers included in active noise and/or vibration control systems.
Generic amplifiers are known for use with active noise and/or vibration control systems. Moreover, active noise and/or vibration control systems (e.g., U.S. Pat. Nos. 5,845,236, 5,754,662, 5,619,581, 5,551,650, 5,526,292, 4,715,559) including error sensors, reference sensors, controllers, amplifiers (e.g., U.S. Pat. No. 5,802,184), and inertial actuators (e.g., U.S. Pat. No. 5,884,736) are known.
The present invention provides over-voltage protection circuits for power supplies that may limit input voltage spikes to a power converter and amplifiers including a damping loop that may damp filter resonance. Active damping systems incorporating the over-voltage protection circuits and/or damping loops of the present invention are also provided which may be particularly advantageous in applications such as aircraft or other vehicle applications where size and power consumption are important design considerations. In various embodiments, the over-voltage protection circuit in various embodiments senses AC and/or DC voltage levels above a detection threshold level and momentarily disconnects the voltage input to thereby reduce the maximum voltage level input transients seen by the power converter. A capacitor may be provided to maintain the input voltage to the power converter while the input is switched out. The amplifier circuit damping loop in various embodiments is nested with a control circuit current feedback loop which may compensate for feedback problems, such as instability, which may result when an inductor-capacitor-inductor (L-C-L) filter is coupled to the output of the amplifier.
In embodiments of the present invention, a power supply includes a voltage source input and a power converter coupled to the voltage source input. A switch is coupled between the voltage source input and the power converter. A controller is coupled to the voltage source input and the switch. The controller opens the switch responsive to detection of a voltage on the voltage source input that exceeds a prescribed limit and closes the switch responsive to detection of a voltage on the voltage source input that does not exceed the prescribed limit to limit over-voltage transients seen by the power converter. The power converter may be a DC to DC converter. The voltage source input may be a DC rail. A capacitor may be coupled between a high side and a low side of the voltage source input.
In further embodiments of the present invention, the voltage source input comprises an AC input and the protection circuit further includes an AC to DC converter coupled between the AC input and the switch. The switch is coupled to the power converter by a DC rail. The controller may be further configured to open the switch responsive to detection of a voltage on the DC rail that exceeds a second prescribed limit to limit over-voltage transients seen by the power converter.
In other embodiments of the present invention, the power supply includes an input voltage sense circuit, having a sense input coupled to the AC input, that outputs an input voltage signal to the controller. The power supply also includes a DC voltage sense circuit having a sense input coupled to the DC rail that outputs a DC voltage signal to the controller. The controller includes a first threshold comparator coupled to the input voltage signal and a second threshold comparator coupled to the DC voltage signal. A switch drive circuit opens and closes the switch responsive to the first and second threshold comparators. A voltage reference signal may be coupled to a reference input of the second threshold comparator and the switch drive circuit may open the switch responsive to the second threshold comparator when the DC voltage signal exceeds the voltage reference signal. The first and second threshold comparators may be hysteretic comparators.
In further embodiments of the present invention, active noise/vibration control systems are provided including at least one reference sensor having a reference signal output representative of a source of disturbance and at least one error sensor having an error signal output representative of a residual disturbance. A controller is coupled to the reference signal output and the error signal output. The controller generates at least one output signal responsive to the reference signal output and the error signal output based on a control method. The control system further includes an amplifier having at least one amplifier channel that amplifies the at least one output signal to provide at least one drive signal. The amplifier includes a voltage source input and a DC to DC power converter coupled to the voltage source input. A switch is coupled between the voltage source input and the power converter. A controller is coupled to the voltage source input and the switch. The controller opens the switch responsive to detection of a voltage on the voltage source input that exceeds a prescribed limit and closes the switch responsive to detection of a voltage on the voltage source input that does not exceed the prescribed limit to limit over-voltage transients seen by the power converter.
In other embodiments of the present invention, an amplifier channel is provided including an L-C filter having an input side and an output side coupled to an output of the amplifier channel. A current loop feedback circuit is coupled between the L-C filter and an input of the amplifier channel. A damping loop is nested within the current loop, the damping loop being configured to dampen resonance from the L-C filter in the current feedback circuit. The L-C filter may be an L-C-L filter. The damping loop may be responsive to a voltage at the output side of the L-C filter or to a main current feedback signal.
In further embodiments of the present invention, the damping loop further includes an amplifier coupled to the main current feedback to provide an active damping loop. The damping loop may also include a differentiating input circuit coupling the main current feedback to the amplifier. The differentiating input circuit may include a resistor and a capacitor in series. The damping loop may also include a current feedback summer coupled to the input side of the L-C filter and a MOSFET H-bridge circuit coupled between the current feedback summer and the differentiating input circuit.
In other embodiments of the present invention, an over-voltage protection circuit adapted for interconnection to an input power line is provided. The circuit includes a DC rail voltage for powering a power device and an input switch for selective connecting or disconnecting the input power line from the DC voltage rail. A switch drive is operatively coupled to the input switch for opening and closing the switch at commanded times. A comparator compares the input voltage of the input power line or DC voltage rail to a prescribed limit set by a voltage reference and upon exceeding said limit, commanding the switch drive to open the input switch thereby disconnecting the input power line from the DC voltage rail and protecting a power device from over-voltage transients.